Process of treating vulcanized rubber.



HANK .v. mama, or nearest, Montana-rs, mama lat-"rumor um umdition in contact with solvents of sulfur, the

raw rubber.

UNITED, sTArrns k assmmrnnrsor omz-mr re um! antenna, or minim, unname- SET'I'B, AND ONE-HALF 'IO wanna wsmns oig orfnoa'mn, mssonuenrre;

rnocnsa or vunomann nunnna,

lam-swing. Application flat! Toall'whom it may concern: I

Be it known that I, FRANK V. ONmui, a citizen of the United States, residing in Boston, county of. Suffolk, and State of Massachusetts, have invented an Improvement in Processes of Treating Vulcanized is a specification.

This invention relates toa process-for the recovery ofrubber from rubber waste.

It is well known that ordinary vulcanized rubber contains sulfur in two distinct states; that free or uncombined andthat chemical] combined with the rubber substance. pon the combined sulfur depend all the properties which distinguish vulcanized from raw or native india rubber, such as pliability, extensibility, ,resiliency, resistance to changes of temperature and insolubility in the well known solvents of raw rubber. If brought in a finely divided confree sulfur may be removed, but the combined sulfur remains and the vulcanized substance is substantially unchanged.

Processes for dissolvin out by chemical means, both the free sul r and the vegetable fiber of rubber waste, are of record, but the products, althou h called devulcanilzed, retain the 'com'ined sulfur and are a poor substitutq jor raw rubben.

. I am aware that-numerous processes have been recorded by; hich it-has been claimedvulcanized rub 1' isnjfan be devulcanized, but which, in fa ii y'iperely remove the free sulfur and soften the rubber, or if capable of bringing the vulcanized rubber into true solution, greatly impair the qualities of the rubber, which condif ion greatly impairs its hibits all thccharac 'istits ofraw rubber, such as the followin (1) It dissolves ;the usual solvents of of commerce, whichis. es

e adication of amen 2min. Patented 16,1917.

inn e n; 191.570... Y

' (2) It does notrulcanizewithout addi- {tion' of sulfur.

(8) Mixed with sulfur it vulcanize e the sameas raw rub r.

(4') Vulcanized, it has the strength, flexi- ,bihty, resiliency,, .et c., ofsoft'yulcanized rub- Rubber, of which the following description ber 'I lie solvent I have best suited-to s irit; that is, rosin fspirit orrosm naphtha my purpose, so, as to excnde r h' snailmg constituents, as will be described. a Commercial rosin irit is ferabl' neutralized with an alka i and si l tilled 31;- rest heat or preferably The dlstlllatiog is eontmiled7mtii theieinperature of the vamrctrises toa0ut"1il0 centig'rade and the ions below, perature are run o'fi' from-the receiver for use. The fractions which 'a'rei-distilled oil at or below about"'130 C. constitute refined rosin s irit, and will be hereinafter referred to as t e solvent.

So 'eflicient is-this solvent, I find it unnecessary to grinti the rubber waste into small particles, ave-has been done by others in reclaiming waste; .In using this solvent, the waste rubber is exposed to'the liquid" at a' temperature .of about 130 C. or a t'emperature high enough to rapidly dissolve'the vulcanized rubber.

and-not igh enoug'h to be detrimental'to the final produot'iof the process. :As this maximum temperature will vary somewhat the practice of my invention is refinedl'roein A ialj 'refinedf-Tor jghofeteamw according to the: original quality of, the' rubber vulcanized, it ma "be readily ascertained by treating ytwo otsof any; given a sample of vulcanizedrubber ofknown cog;- position; one at a Ziemperature above and one below 130 0. "If the rubber recovered at the higher heat is more sticky and less elastic than the other lot, andwhen vulcanized is weaker and less flexible and resilient, then the maximum temperature has been exceeded and the true maximum is found by continued comparison For the best results, a detrimental temperature should not'be reached at any stage of the process. 4

During the solution of the rubber waste, the solvent exerts considerable tension or pressure, and thisstage of the process should consists in digesting the 'rubbelf ivd temperature not injurious to the-'fi 1o,

digesler under prssure .a nd a tmjqera:

ture below that detrimental t .vt-he .r ubber product; with refind rbsin sjiil l' h'zyyir gg boiling point below a tempe'l a 'uie (let-r1 mental to the rubber.

9. The process of 1'eclzun11 1 1 eratlng rubber fmfil rubber 'wasfie net and until t.he vulcanized rqbb'r s. 1 solvgl, with 1 refined rosin s'pir1t,-L.mqchgn "cally 'separdting the rubber solufcipn fro thgl impurities pf the rubber waste, he atih I mew this specification in the presence of the rubber solution in mstill y y means ofsteam forced thmugh tbs; rubber solution therein, removinglthe Rubber from the'still body, and mechanically separating the wa- -ter thsre'ftom; and 'finally'heutin'g the rubbenthustreated in uj'vacuum chamber.

In testimony whereof; I have signed my twb; 3 subscribing Witnesses.

iI FRA 'NK ONIBILL 

